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2005 FORESTER TURBO AUTOMATIC
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3 Posts
Discussion Starter · #1 ·
Hi,

I've been running Mobil 1 5w30 on a yearly extended il change schedule.
I use a wix filter and change it every 6 months and top off the oil. My yearly milage is 10 k a year.

Recently I have been told that the turbo chews up 5w30 something awful shearing it to 20 weight in no time. It was suggested I change over to Mobile 0W40 instead. Would the 40wt oil be too thick to provide adequate lubrication in small passages?

Anyone have any insights please help
 

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2004 FXT 5MT
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476 Posts
Plenty of people use Shell Rotella T6 5w-40 in their turbo subarus, all you have to do is search it and you will see. The Mobil 0w40 is another good choice, I am switching my FXT to it this week, from Rotella T6.
I run T6 in my wife's Legacy GT.

Both great oils.

You can always send your current oil in for analysis and see what kind of results you get back. 10k miles on M1 5W30 doesnt sound too great from what I have read, but obviously your car is still running.
 

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2004 FXT / 2020 Outback Onyx XT
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1,682 Posts
No, it's not too thick and your owner's manual allows 10W-40 down to -4F! I generally do not recommend Resource Conserving oils (like Mobil1 5W-30/0W-30) in turbos, but I'm wondering if 0W-40 would be a little too thick at start up in ND?

Do you ever have unassisted (no block heater, not garaged, etc.) cold starts during winter? German Castrol Syntec (GC) 0W-30 should be a little thinner at start up than M1 0W-40 and it is a robust 30 grade oil. Another option is to perhaps mix in some Mobil1 0W-30 to thin out the 0W-40.

As bad as most of us (myself included) bash Resource Conserving oils for shearing to 20 grades in most turbo, and sometimes even N/A applications, your location may dictate that you run a thinner oil in winter than most of us.

The MRV on M1 0W-40 is 31,000 cP at -40C and Mobil1 0W-30 has an MRV of 13,250 cP so the 0W-30 is much thinner in extreme cold. The HTHS on M1 0W-40 is 3.8 so thinning it out with two quarts of 0W-30 should still give you decent turbo and bearing protection with an HTHS of 3.48-ish. I have seen one uoa on a Stage I FXT running straight M1 0W-30 and the oil actually held up well. It was only one uoa though and M1 30 grade uoa's are a bit rare since everyone is afraid to use it! OTOH, a strong battery could play a more important part of how quickly your car starts in winter than the oil you use.

domo - I believe that he changes it twice a year making 5k on the oil interval and 10k on the car annually.

-Dennis
 

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2019 Crosstrek 2018 Forester XT
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15,013 Posts
German Castrol (GC) 0W-30 is a great choice.
 

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2005 FORESTER TURBO AUTOMATIC
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3 Posts
Discussion Starter · #5 ·
What I meant is my yearly milage is no more than 10k. Winter starts the car is garaged.

Would 15-40 over the summer months conventional motor oil be a consideration?
 

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'21 ISM Crosstrek Limited
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2004 FXT / 2020 Outback Onyx XT
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What I meant is my yearly milage is no more than 10k. Winter starts the car is garaged.

Would 15-40 over the summer months conventional motor oil be a consideration?
No, stick with "synthetic". We've all mentioned German Castrol 0W-30 because it's a robust 30 grade with higher anti-wear additive levels and is robust enough to meet European ACEA A3 and many Euro manufacturer specs, including MB 229.5, one of the toughest to meet.

-Dennis


Sent from AutoGuide.com App
 

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2012 Outback CVT
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79 Posts
The Mobil 1, 0w-40 would be better for a turbocharged engine year round. It too will shear down, but only to a 30 weight. The Mobil 1, 0w-40 also has a much more robust additive chemistry compared to the regular Mobil 1, 5w-30 (significantly higher levels of antiwear and detergent/dispersant additives). So it will simply hold up better in the application. Turbocharged engines are also prone to excessive fuel dilution of the engine oil under certain conditions (short trip driving, cold weather use) and this further thins out the oil.

TS
 
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